1. Field of the Invention
The present invention relates to a safety catch device for elevator cars guided on at least one guide rail. The safety catch device includes a braking device acting on the guide rail for braking the elevator car and a control device for controlling the braking force of the braking device in dependence on the load and/or deceleration.
2. Description of the Related Art
Safety catch devices used in elevators usually act independently of the load. The braking forces are applied by means of fixedly adjusted springs which apply the same forces on the rail in the case of an empty car as in the case of a full car after the cables have failed. This results in undesirably high decelerations when the elevator car is empty or contains only a small load.
In order to avoid the undesirably high decelerations or braking accelerations in the case of no load or a small load in the elevator car, it is necessary to control the braking forces in dependence on the load or deceleration.
DE-A-39 34 492 and EP-A-0 183 616 disclose controls for the application of braking forces of an elevator car in which the braking forces are controlled either hydraulically or electromagnetically. However, such controls require a complicated apparatus and may be susceptible to trouble.